Measurement of the double polarization observable E in the reaction vector (γ) vector p → pη'

The study of η'-photoproduction off protons allows an investigation of the not well understood high-lying resonances (mN* > 1892 MeV) of the nucleon excitation spectrum. The recent cross section data measured at CLAS and CBELSA/TAPS alone are not sufficient in order to disentangle all the different resonance contributions due to the largely overlapping resonances. Additionally, the measurement of well chosen single and double polarization observables is needed for an unambiguous solution. Several of these polarization observables are measured with the CBELSA/TAPS experiment, utilizing a polarized photon beam and polarized nucleons. The setup provides a nearly full 4π angular coverage and a high detection efficiency for neutral final states. In this talk, the preliminary results of the double polarization observable E in the reaction vector (γ) vector p → η'p, using a circularly polarized photon beam in combination with a longitudinally polarized butanol target, will be presented.